1. Field of the Invention
The present invention relates to the setting of transmission/reception frequencies in a radio control apparatus for remotely controlling devices such as model airplanes, automobiles, boats, etc.
2. Description of the Related Art
To carry out transmission in a conventional radio controlling apparatus, a high frequency circuit for determining a transmission frequency band and a type of carrier wave is utilized. Pulse Position Modulation (PPM) or Pulse Code Modulation (PCM) signal systems are used in conjunction with amplitude or frequency modulation of the carrier wave.
Regarding such frequencies for a radio controlling apparatus, usable frequency bands and frequencies in the frequency bands are controlled under the Radio Law of each country. In Japan, for example, in the frequency band of 27 MHz, the range of frequencies from 26.995 MHz to 27.245 MHz is divided into six bands, at intervals of 50 KHz. However, 27.245 MHz and 27.255 MHz are used as a common band. In the frequency band of 40 MHz, the range of frequencies from 40.61 MHz to 40.85 MHz is divided into thirteen bands, at intervals of 20 KHz. In the United States, in the frequency band of 72 MHz, the frequency range of 72.01 MHz to 72.99 MHz is divided into fifty bands, at intervals of 20 KHz. In Germany, the frequency of the radio controlling apparatus for a model is defined under its Radio Law.
In particular, self-imposed control on the frequency band of 40 MHz is provided under the Recommendation Standard and Adaptation Certified and Recognized Standard (Notification No. 895 of the Ministry of Posts and Telecommunications, Nov. 24, 1984) in Japan. This self-imposed control is required to be satisfied. Because the self-imposed control defines that xe2x80x9can oscillation system should be a crystal oscillation system,xe2x80x9d a Phase-Locked Loop (PLL) circuit cannot be used in the frequency band of 40 MHz. Although nine more channels are allowed to be used in the band of 72 MHz, each channel is changed on the basis of a crystal exchanging system, wherein a high frequency circuit-designed in modules and with frequencies assigned to each countryxe2x80x94is utilized in a radio controlling apparatus. In general, the frequency of a carrier wave is changed by exchanging crystal oscillators. On the other hand, many countries allow the use of PLL circuits, but the use differs depending on the Radio Law of each country. When a PLL circuit is used, the changing and setting of the frequency can be easily accomplished in a radio communication apparatus.
FIG. 8 is a block diagram showing an example of a conventional radio controlling transmission apparatus. Voltage values, which are obtained by the operation of elements 2A, 2B, 2C and 2D, are brought to input terminals of a multiplexer, respectively. From the output of the multiplexer, the voltage values pass through an A/D converter, and parallel output signals from the A/D converter are applied to a parallel-serial converter. Addresses of the operational elements 2A, 2B, 2C and 2D are read sequentially and converted to serial data, so that a carrier wave is FSK modulated and transmitted.
An example of the serial signal will be explained with reference to time charts shown in FIG. 7. This figure shows a signal sequence obtained by the operation of eight operational elements, wherein one frame is set at 22.5 msec. An one shot pulse width T2 of a rise portion according to the control of each signal is a variable value of 450 xcexcsec to 950 xcexcsec, and a channel pulse period T4 is 1520 xcexcsec. Although each one shot pulse varies depending on the amount of control; the bands of reset pulse widths T3 and T3xe2x80x2 are set to at least 5 msec at the minimum. Since control data is updated every one frame, or 22.5 msec, smooth control can be performed.
Since radio control is frequently performed with a small number of channels at a specific location, there is the problem of radio interference, which causes an uncontrollable state in the devices to be controlled. Various designs are disclosed in the prior art to avoid such radio interference. For example, unexamined Japanese Patent Publication No. Hei 34891 discloses a band detector for detecting whether or not a channel, which is to be controlled by a radio controlling apparatus at a control start time, is used by another apparatus. The band detector makes its detection before the control is performed. If a desired control channel is in use, the band detector outputs an alarm signal and turns on a red light-emitting diode to inform that the channel is in use. If the desired control is in a vacant channel, the band detector turns on a green light-emitting diode to inform that the channel is not in use. This allows the channel to be changed smoothly.
However, working frequencies are limited in radio controlling apparatus. Six bands are assigned to the frequency band of 27 MHz, thirteen bands are assigned to the frequency band of 40 MHz, and nine bands are assigned to the band of 70 MHz. Model airplanes and helicopters using a radio controlling apparatus can only be operated at limited locations. In addition, at such a location, there is the danger that they may crush or plunge into a crowd due to the occurrence of an uncontrollable state. A case in which an uncontrollable state occurs because of radio interference with the radio controlling apparatus increases with beginners who are not familiar with the control of the apparatus. An object of the present invention is to provide a radio controlling apparatus, which changes a channel being interfered to a vacant channel rapidly and allows smooth control even if an uncontrollable state suddenly occurs.
According to the present invention, there is provided a radio controlling apparatus which includes an operation section including a joy stick; a control section having a central processing unit (CPU) and memory; a radio controlling transmission apparatus having a transmission section for transmitting control signals based on an operation of the operation section; and a controlled apparatus, which is controlled by receiving the transmitted control signals and converts the received signals to parallel signals that control controlled portions. When an uncontrollable state of a transmission channel occurs in the radio controlling transmission apparatus due to radio interference, the radio controlling apparatus utilizes a reception section for searching a vacant channel, which is used to change a channel being used to the vacant channel.
The radio controlling transmission apparatus includes a mechanism for setting a selection code transmission timer for assigning a control signal transmission time, a selection code transmission time and a reception section reception time, so as to transmit a selection code that distinguishes the control signals of the controlled apparatus from control signals of another apparatus at the selection code transmission time.
Further, the reception section for searching a vacant channel of the radio controlling transmission apparatus includes a vacant channel searching mechanism for searching a vacant channel during the duration of the reception time and for changing the channel and searching for another channel at the next reception time if there is no vacant channel, and a vacant channel transmitting mechanism for transmitting channel data at the next reception time when the vacant channel of the memory is rewritten. The vacant channel is stored in the memory of the control section.
The controlled apparatus includes a section for detecting a selection code from received signals, memory for storing the detected selection code, and a squelch mechanism for setting a selection code holding timer, which determines a detection interval of the selection code, and for holding a squelch state so as to output control signals for the duration of the selection code holding timer in which the selection code is held.
The controlled apparatus includes a vacant channel holding mechanism for storing or rewriting channel data of the memory storing vacant channels when there is a vacant channel data in the received signals. When the selection code holding time is over during the reception of the control signals and a squelch capability stops, the reception channel is automatically changed to a vacant channel stored in the channel data of the memory and an abnormal operation by which control abnormality is visibly recognized is executed. If there is the selection code in the signals received by the reception section, a squelch capability is exerted so that a controlled state is set.
When the radio controlling transmission apparatus detects control abnormality of the controlled apparatus during the control of the controlled apparatus performed by the operation of the control section, a channel change switch is operated to perform a change to a vacant channel stored in the memory, and an identification code is transmitted to restart control of the controlled apparatus.
Moreover, to prevent radio interference, a continuous tone controlled squelch system (CTCSS) or digital code squelch (DCS) system is used as the selection code to control the controlled section of the radio controlling apparatus by a squelch signal.
FIG. 1 is a block diagram showing a configuration of a radio controlling transmission apparatus according to an embodiment of the present invention, FIG. 1(a) is a block diagram of a radio controlling transmission apparatus, and FIG. 1(b) is a block diagram of a controlled apparatus controlled by the radio controlling transmission apparatus;
FIG. 2 is a flowchart showing an operation of the radio controlling transmission apparatus according to an embodiment of the present invention;
FIG. 3 is a flowchart showing an operation of the controlled apparatus according to an embodiment of the present invention;
FIG. 4 is an outline view showing an example of the radio controlling transmission apparatus;
FIG. 5 is a configuration view for explaining a case in which a controlled apparatus is a model airplane;
FIG. 6 is a time chart showing a time series of a selection code transmission timer;
FIG. 7(a) and FIG. 7(b) are time charts for explaining a case in which FSK modulation is carried out using PPM signal; and
FIG. 8 is a block diagram showing a schematic configuration of a conventional radio controlling transmission apparatus.